Facsimile systems have seen increased acceptance in recent years and, in fact, have become a staple of the business community. In the early days of facsimile systems, some difficulties arose due to incompatibilities of the various systems. Even though one owned a facsimile system, there was some doubt as to whether a facsimile transmission could be completed to another system manufactured by a different manufacturer. This problem was somewhat alleviated when the standards were developed, one of those standards being the Group II standard.
Facsimile protocols are generally comprised of header information that is transmitted to a destination fax followed by an image, this typically being a bit-map image. However, prior to transmitting the header and images, it is necessary for a facsimile machine to negotiate a communication link with the destination facsimile machine. This is typically achieved to some type of hand-shaking. With Group II fax protocol, all too often the originating facsimile machines fail to even negotiate a communication link with the receiving facsimile machine.
When the Group III protocol was introduced in the mid-1980's, the use of facsimile machines saw a rapid increase in use. This was due to the fact that the Group m protocol not only was backward compatible with Group II, but it enabled a high level of standardization to occur in the industry. Typically, a Group m facsimile has associated therewith a handshake protocol that allows the two facsimile machines to determine their combined speed of operation and then transmit the images at that determined or negotiated speed. This is an interesting aspect of the facsimile machine, in that facsimile machines are typically rated at 14.4 Kbs, but this is their maximum speed. All too often, due to noise on the phone line, etc., the facsimile machines will default down to a slower speed. Typically, they initially try to effect the communication link at 9,600 Kbs and then drop to 4,800 Kbs, then 2,400 Kbs, 1,200 Kbs, and so forth, until an error free speed is reached. It is feasible with very noisy lines that a facsimile system may communicate at as low a baud rate as 300 Kbs. However, once an acceptable noise-free communication link can be maintained, then the image is transmitted at that speed, with both the source and destination adjusting their speed to the same speed.
In a Group III fax, the transmission of the image over the negotiated transmission link will consist of first transmitting the header and then all of the pages in the original facsimile document as a single job. Typically, there is an End of Page (EOP) command sent at the end of each page and then an End of Job (EOJ) command sent at the end of the job. During transmission, there are various error correction algorithms utilized to correct the data when it is transmitted, but some applications of the Group III fax has one disadvantage in that if the last page is not received correctly by a receiving fax, it does not provide an acknowledgment to the sending fax that it has received the entire job and the sending fax may interpret this to require a re-send operation, wherein the entire document is re-sent. For small jobs that are only one or two pages long, this is not a problem. However, for large jobs in excess of two hundred pages, this can be quite time consuming. The time consuming aspect is, of course, the time it takes to transmit a single page.
Transmission of an image over a facsimile connection is facilitated by first converting the image into a bit-mapped image via scanning of a hard copy of the document or converting a print job in a computer directly to the image, and then transmitting the individual bits as they are scanned or generated in a serial manner. However, this transmission of images is time consuming, especially if the image includes a lot of dark areas. One solution to this has been to actually transmit the data file prior to transforming it into an image. For example, one system that has achieved this is referred to as the Microsoft Exchange Server®, which is an operating system for messaging and file sharing. The purpose of this system to alleviate the necessity to transfer a document into an image prior to transmission to a remote site. It is not the conversion into the image that is time consuming but, rather, it is the transmission of the image information. Further, on the receiving end, the image information is not readily translated into a data file that can be manipulated. For example, if a destination user desired to transmit a contract which basically comprised an ASCII file, the procedure is to convert it first into an image and then transmit the image to the destination system. Once the destination system receives this image, it must be printed out from a facsimile machine or, alternatively, it can be imported into a computer program which can then either print the image out on a standard printer or store the image. However, once the image is received, it is not in a useable form to allow modification of the document itself With the digital transmission systems, the file itself can be transmitted without first converting it into an image. However, all facsimile systems that exist at present require conversion of a file into an image as it would appear in a printed document and then transmission of this image. This can be facilitated by fax modems that directly convert a file into an image while using a scanner, the scanner being the more conventional approach.